This study examined achievements and limitations of the activitycentered Korean language instruction focusing on Ms. Kim's expository writing lessons in the free semester. Through Ms. Kim's class, students were able to acquire various knowledge of topic subjects and practical knowledge for expository writing. Therefore, activity-centered instruction is a teaching and learning method that is matching for the goal of Korean language arts. However, Ms. Kim’s lessons had limitations in achieving learning goals. The gap between learning goals and actual student-activities was prominent, and topic contents was higher rather than writing strategies. The guidance on writing results was higher rather than writing processes. And the connectivity among activities was found to be insufficient. It is necessary to increase the closeness between the learning goals and the student activities, and balance student and teacher activities.